The present invention directs to an apparatus for detecting a break in a warp yarn in a loom in which shedding operation is performed by resin healds.
Generally, a break in a warp yarn is detected by a dropper mechanism which is disposed in a traveling path of warp yarns between a yarn beam and a heald frame. In the dropper mechanism, a number of warp yarns, for example, more than 8,000 warp yarns, has to be set in such a manner that each warp yarn is passed through the corresponding dropper. Passing of warp yarns through the droppers is a troublesome work, and the loom is complicated by the presence of the dropper mechanism. In order to overcome such problems, there are proposed various types of apparatuses for detecting a break in a warp yarn using a heald through which a warp yarn is passed.
An apparatus for detecting a break in a warp yarn is disclosed in Japanese Patent Application Publication No. 5-302241. The apparatus includes an upper heald bar as an upper carrier rod and a lower heald bar as a lower carrier rod. The upper heald bar has a main body which is made of a conductive material and a part of which is exposed and the rest of which is coated with a non-conductive material. The lower heald bar is made of a conductive material. The upper heald bar has at an end thereof a terminal that is movable with the upper heald bar and contactable with a stationary terminal when the upper heald bar is lowered. These terminals form a timing control circuit. The heald made of conductive material such as a stainless steel are passed at the opposite ends thereof through the upper and lower heald bars. In the above structure, when a warp yarn passed through an eye hole of a heald is broken and then the heald is dropped to the lowermost position, the heald is brought into contact with both of the exposed conductive part of the upper heald bar and the lower heald bar made of a conductive material. Simultaneously, the terminal of the upper heald bar is brought into contact with the stationary terminal, thereby closing the timing control circuit. Thus, a break in a warp yarn is detected, and then the loom operation is stopped, accordingly.
The heald made of a conductive material is a relatively heavy in weight and, therefore, the heald tends to overrun due to the inertial force of the heald generated while the heald frame is moving vertically. Thus, there is a fear that the heald is brought into contact with the conductive parts of the upper and lower heald bars when the heald is lowered. In recent weaving looms operating at an increased speed of about 1,000 rpm, the apparatus of the above Publication may fail to detect the break properly. Thus, the apparatus is difficult to be put into practical use. Additionally, the apparatus of the above Publication is complicated in structure and hence expensive.
The present invention which has been made in light of the above problems is directed to an apparatus for detecting a break in a warp yarn which has a simple structure and is capable of reliably detecting a break in a warp yarn by using a deformable characteristics of the resin heald.